Direct measurement of anisotropic probe motion in ordered systems

Summary form only given.Conventional fluorescence polarization experiments are in general sensitive to only one degree of angular freedom in the laboratory frame. Using a variable excitation polarization, it is possible to photoselect a range of initial nonequilibrium molecular orientations in an anisotropic medium that are sensitive to both /spl theta/ and /spl phi/ motions, and whose evolution can be monitored by picosecond time-resolved polarized fluorescence. We have made direct measurements of probe /spl theta/ and /spl phi/ diffusion in an ordered medium. Our results indicate that the dynamics are dominated by anisotropic viscosity, which increases for /spl phi/ motion as the liquid crystal order relaxes.